ISHS Acta Horticulturae 662: VII International Symposium on Temperate Zone Fruits in the Tropics and Subtropics
PHYSIOLOGICAL AND ANATOMICAL ASPECTS OF ABSCISSION AND CHEMICAL CONTROL OF FLOWER AND FRUIT DROP IN APPLE |
| Authors: | V.K. Pandita, K.K. Jindal |
| Keywords: | abscission, hormonal control, hydrolytic enzymes, ultrastructure |
| Abstract:
Leaf abscission studies were carried on potted plants of one-year-old Starking Delicious apples grafted on MM106 rootstock. About 30 cm long shoots were selected wherein 7 leaves were maintained at equal distance. The 4th leaf was fed with 74KBq 14C-IAA. On the 3rd day of 14C-IAA application the shoots were sprayed with ethrel to induce abscission. Translocation of 14C-IAA activity from fed leaf increased till ethylene application, but following ethylene treatment, the activity in the leaves decreased. Prior to ethylene treatment, the gradient of 14C-IAA activity was more towards distal region but with ethylene treatment the gradient was reversed and shifted towards proximal region of abscission zone. The enhancement of leaf abscission zone formation with ethylene treatment caused an increase in soluble proteins, endo-cellulase, and exo-polygalacturonase and peroxidase activities. Ultra-structural studies indicated that petiole/stem abscission zone in leaves consisted of loose distal region and compact proximal region. The separation of cells in distal region occurred due to dissolution of middle lamella. Intercellular changes included electron dense areas in cytoplasm, increase in rough endoplasmic reticulum (RER) and dictyosomes. Cell wall degradation occurred near plasmodesmata. In another experiment 9-year-old Starking Delicious/M7 apple trees were sprayed with different concentrations of NAA, GA3, ethrel and PP333. GA3 application improved fruit set/cm limb circumference whereas NAA and ethrel application reduced it. GA3 application also reduced fruit drop significantly over control. | |
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